This invention lies in the field of the production of petroleum liquids and gases from deep geologic formations.
More particularly it lies in the field of production of petroleum liquids and gasses from formations of low permeability where the formations must be hydraulically fractured in order to get economic hydrocarbon flow.
Still more particularly it lies in the field of methods and apparatus for determining the azimuth and length of deep vertical fractures in the earth.
Recent work in seismic prospecting has involved improved methods of analyzing field records of reflections received from reflection at the top of certain formations where there is a condition of gas saturated liquids in the pores of the formation. This situation is conventionally known as "bright spot". So far this has only been applied to the recognition of locations in the earth where this condition pre-exists.
My invention in copending application Ser. No. 268,787, involves the step or steps of injecting a selected fluid into a formation to create this condition, where it did not exist before, so as to make visible by seismic waves the presence, in certain locations in the formation, where such "bright spot" conditions had been generated.
My U.S. Pat. Nos. 4,282,587 and 4,280,200 teach the use of these methods in applications involving shallow formations.
The application applies these techniques to the problems of determining azimuths and lengths of deep vertical fractures.